This invention relates to an apparatus for producing synchrotron orbital radiation (abbreviated and hereinafter referred to as an SOR apparatus). More particularly, it relates to improvements in a superconducting SOR apparatus.
Synchrotron orbital radiation is a form of electromagnetic energy which is emitted by charged particles in circular motion at relativistic speeds. Because of its high intensity, high degree of collimation, broad bandwidth, high polarization, and other properties, it is highly useful for experiments in a wide range of scientific fields, and there is accordingly a great demand for an SOR appratus which is smaller and more economical to enable its use by an increased number of researchers.
FIGS. 1 through 3 illustrate a conventional SOR apparatus which is described in "Superconducting Racetrack Electron Storage Ring and Coexistent Injector Microtron for Synchrotron Radiation" by Yoshikazu Miyahara et al. in Technical Report of ISSP, September, 1984, published by the University of Tokyo Institute for Solid State Physics. As shown in FIG. 1, two superconducting deflecting electromagnets 1 are disposed along a loop-shaped vacuum chamber 2 through which charged particles pass. A high vacuum is maintained with the vacuum chamber 2 so that the charged particles inside it will not lose energy by colliding with particles in the air. The deflecting electromagnets 1 produce magnetic fields which bend the paths of motion of the charged particles and cause them to travel along a curved path. Four quadrupole electromagnets 3 are disposed along the vacuum chamber 2 between the two deflecting electromagnets 1, and a high-frequency accelerating cavity 4 is disposed along the vacuum chamber 2 between two of the quadrupole electromagnets 3. The quadrupole electromagnets 3 are used to force the charged particles with the vacuum chamber 2 to converge, and the high-frequency acceleration cavity 4 is used to accelerate the charged particles.
As shown in FIG. 2, which is a schematic cross-sectional view of the SOR apparatus of FIG. 1, each deflecting electromagnet 1 contains an upper superconducting coil 5a and a lower superconducting coil 5b which are disposed above and below, respectively, the vacuum chamber 2. To produce vertically-directed magnetic fields, the upper and lower coils 5a and 5b are each immersed in a separate helium tank 6 containing liquid helium 14 which cools the coils 5 to cryogenic temperatures. Each helium tank 6 is surrounded by a corresponding nitrogen shield 7 which serves to prevent heat from penetrating to the helium tank 6. A nitrogen tank 8 containing liquid nitrogen 15 is mounted atop each nitrogen shield 7 and serves to cool the nitrogen shield 7 to the temperature of liquid nitrogen. Each nitrogen shield 7 and nitrogen tank 8 is surrounded by a corresponding vacuum tank 9 inside of which a vacuum is maintained so as to thermally insulate the members contained therein.
The upper portion of each helium tank 6 is penetrated by a liquid helium supply pipe 10 through which liquid helium 14 can be supplied thereto and a helium gas exhaust pipe 11 through which helium gas can be exhausted. Similarly, the upper portion of each nitrogen tank 8 is penetrated by a liquid nitrogen supply pipe 12 through which liquid nitrogen 15 can be supplied thereto and a nitrogen gas exhaust pipe 13 through which nitrogen gas can be exhausted. The supply pipes pass through the walls of the vacuum tanks 9 and are connected to unillustrated sources of liquid helium and liquid nitrogen.
As shown in FIG. 3, which is a schematic diagram of the electrical connections of the superconducting coils 5, the upper coil 5a and the lower coil 5b of each deflecting electromagnet 1 are connected in series to a separate power supply 16. The two power supplies 16 are controlled by a controller 17 in a manner such that the magnetic fields produced by the left and right coils 5 will be equal in strength.
In the operation of a conventional superconducting SOR apparatus, a beam of charged particles which is stored within the vacuum chamber 2 is bent by the deflecting electromagnets 1 and is caused to travel along a closed path within the vacuum chamber 2. The magnetic fields generated by the deflecting electromagnets 1 produce an infinite number of closed paths, but the charged particles are prevented from diverging by the quadrupole magnets 3 which force them to converge. When the paths of motion of the charged particles are curved by the deflecting electromagnets 1, the particles emit synchrotron orbital radiation in the direction of motion. The energy which the charged particles lose due to this radiation is replenished by the high-frequency acceleration cavity 4 so that the charged particles maintain their kinetic energy and can be stored in motion for long periods of time.
The conventional SOR apparatus illustrated in FIGS. 1 through 3 has the drawback that liquid helium must be separately supplied to each of the helium tanks 6, and liquid nitrogen must be separately supplied to each of the nitrogen tanks 8 via the supply pipes 10 and 12. As a result, the supplying of liquid nitrogen and liquid helium is troublesome and the cooling efficiency of the apparatus is poor.
Furthermore, as shown in FIG. 3, a conventional apparatus requires a separate power supply 16 for each deflecting electromagnetic 1 and a controller 17 which controls all of the power supplies 16 so that the coils 5 will produce magnetic fields of equal strength. The necessity for separate power supplies 16 and a controller 17 increases the cost of the apparatus.